This invention relates to slurries of fine abrasive and their use.
Polishing operations are commonly performed by continuously feeding an excess of a fine abrasive-lubricant slurry to the entire surface of a rotary flat lap while forcing a workpiece against the slurry-covered surface. This process understandably wears away the lap surface, which must be periodically refinished. Many particles slide off the lapping surface too quickly to be used. Since the slurry is usually recirculated to minimize cost, the initially fine abrasive particles become even smaller as they are used, resulting in decreased abrading efficiency and a constantly changing finish on the workpiece.
Fine abrasive particles are also difficult to use in coated abrasive structures. It is difficult to prepare a product having consistent abrading features; further, the surface grain dulls during use and the lower-situated grain remains out of contact with the workpiece, the coating thickness typically being twice the diameter of each individual grain. Extremely small abrasive grains, e.g., 3-micron particles, are present in such thin abrasive coatings that the entire coated abrasive structure may be destroyed as the result of inadvertent gouging or snagging. Where the backing is cloth, such grains may also be forced into the backing rather than into the workpiece.
Effective utilization of fine abrasive grains has thus always posed a problem to manufacturers and users of both polishing slurries and coated abrasive products. One method of using fine particles has been to disperse the particles in a softer, lower-melting inorganic material to form a composite granule; see U.S. Pat. No. 2,849,305 in which titanium carbide grains are dispersed in a fused alumina-titania matrix and the resulting composite crushed and cooled.